Negative Split a 3:15 Marathon (Read 693 times)

I would like to try to negative split my upcoming marathon. I would like to complete the race in 3:15. This will be my first marathon and I'm not sure how fast I should run each mile. I'm afraid to start too slow or too fast. I don't want to make up too much lost time or crash. Do anyone have some advice?

Biking Bad

finnegan begin again

posted: 12/14/2012 at 6:21 PMmodified: 12/14/2012 at 6:32 PM

See my Erie marathon splits. Did a 1:32 half marathon solo time trial a couple of weeks before which really was the confidence builder.

MTA: I can't stress pre race and in race hydration from start to finish enough. For me anyway. Alternating water and sugar sports drinks. About 4-5 Gu's as well.

Your 30 k looked good

"... the harder the conflict, the more glorious the triumph. What we obtain too cheap, we esteem too lightly: it is dearness only that gives every thing its value..." Thomas Paine Dec 23, 1776 The Crisis

I don't understand the question. If you want to negative split by, say 2 minutes, then you just run the first half at 3:16 pace (7:29 per mile) and the second half at 3:14 pace (7:24 per mile). That's an easy calculation. But why do you want to intentionally run slower that you can?

I don't understand the question. If you want to negative split by, say 2 minutes, then you just run the first half at 3:16 pace (7:29 per mile) and the second half at 3:14 pace (7:24 per mile). That's an easy calculation. But why do you want to intentionally run slower that you can?

I want to see how others did it. Some may use the method you mentioned and other may choose a different approach. I'm just curious.

Also, I'm not sure I will run intentionally slower than I can. This is my first marathon and I have no idea how it will go.

I think I will run a few seconds slower per mile in the first half. Once I get past the first half, I plan to pick it up the pace a little. I will see how I feel at mile 20 and crank it up if I feel good.

I'll be happy to finish, but, I'm going for 3:15. in the past, negative splits have been more enjoyable than positive splits. This is why I'm curious.

Wouldn't you just do what you did in that last (impressive) 30KM workout in your log, add 10KM with some fade and you're home with your time and you're negative split?

That's the plan. The plan I had for the 30K was not to race it 100%. Instead, I started with an intentional warm-up for 4.6 and run 14 close to MP. It is hot and humid in Houston. I felt great and did the last two at tempo. I completed the race with plenty of gas. I will definitely start my marathon faster than I did at my recent 30K. I'm thinking 7:30-7:35 pace. My average needs to be 7:26 for the 3:15.

I think I will run a few seconds slower per mile in the first half. Once I get past the first half, I plan to pick it up the pace a little. I will see how I feel at mile 20 and crank it up if I feel good.

I've gone 0/3 on that. It's amazing to feel like you've cranked up you're pace. Only to realize you are barely keeping pace. People aren't kidding when they say the first half of the race is the first 20 miles. That last 10k can be a bear.

What's the target race?

"... the harder the conflict, the more glorious the triumph. What we obtain too cheap, we esteem too lightly: it is dearness only that gives every thing its value..." Thomas Paine Dec 23, 1776 The Crisis

I want to see how others did it. Some may use the method you mentioned and other may choose a different approach. I'm just curious.

I run a lot of negative splits -- I mean, I've probably run 50+ negative-split marathons -- and that's basically what I do, unless the course profile is really wonky. I also tend to round to the nearest 5-second pace, to make the mental math easier. Running 3:20 this way is nice: it's 7:40 first half, 7:35 second half. Last weekend I planned 6:50 first half, 6:45 second half, for 2:58. I didn't quite hold on to that, but I was close, and still negative split.

3:15 doesn't work quite that well -- if you run 7:30 the first half and 7:25 the second, you'll be a little short. The few times I've paced for 3:15ish I believe I've tended to try 7:30 / 7:20, which is a bit faster.

That's the plan. The plan I had for the 30K was not to race it 100%. Instead, I started with an intentional warm-up for 4.6 and run 14 close to MP. It is hot and humid in Houston. I felt great and did the last two at tempo. I completed the race with plenty of gas. I will definitely start my marathon faster than I did at my recent 30K. I'm thinking 7:30-7:35 pace. My average needs to be 7:26 for the 3:15.

If your average needs to be 7:26, Then the most efficient pace for the whole race (if you can hold it) is 7:26. The reality is that most non-elite runners do not have the percent muscle mass (or the efficient liver function) that will allow them to have a level of glycogen that will last for the whole 26.2 miles. We start burning more and more musclefat(rather than the glycogen in the muscle) for energy as the race goes on. MuscleFatfor energy requires 20% more oxygen to produce the same level of energy – so as the race goes on it will be harder to hold that pace. That’s why, unless you are starting the race much slower than your “perfect” pace it will be hard to hold that pace thru the full marathon

Edited to say fat instead of muscle - must have been using the fat in my body to think rather than the grey matter. Thanks for the correction guys.

Perhaps an expert will correct me, but I don't believe we burn a significant amount of muscle in a marathon. We do burn more fat as glycogen stores deplete.

Logic says that you're right; lowered glycogen stores make it harder to run as fast late in a race. But in practice, negative splits are an effective strategy, for amateurs as well as elites. Attempting to run a slight negative split is a more conservative strategy than trying for strictly even splits, because if you're a little wrong in your estimate, the potential blowup is not as bad. 7:30 / 7:30 pace instead of a desired 7:30 / 7:25 is a lot better than 7:27.5 / 7:45.

I run a lot of negative splits -- I mean, I've probably run 50+ negative-split marathons -- and that's basically what I do, unless the course profile is really wonky. I also tend to round to the nearest 5-second pace, to make the mental math easier. Running 3:20 this way is nice: it's 7:40 first half, 7:35 second half. Last weekend I planned 6:50 first half, 6:45 second half, for 2:58. I didn't quite hold on to that, but I was close, and still negative split.

3:15 doesn't work quite that well -- if you run 7:30 the first half and 7:25 the second, you'll be a little short. The few times I've paced for 3:15ish I believe I've tended to try 7:30 / 7:20, which is a bit faster.

Bob -- how do you typically execute the change from your frontside pace to your back half pace? Is it a definitely gear change when you hit the 1/2 mark, or steady speed up over the next split (or few?)?

I've done my best to live the right way. I get up every morning and go to work each day. (for now)

It's probably not optimal, but yeah, it's 13 miles at a slower pace, then bam, the rest at the faster pace. A 5-second change in pace is not that big a deal, at M13. It's holding it that's the problem!

Boston is really the only race where I do anything differently -- because of the course profile, and the fact that it's often a goal race, I generally make a custom paceband. But the paces still start with the assumption of a particular negative split, and the average pace picks up at the half.

I always targeting kind of "even efforts" splits. I ran with a negative split my last marathon, but it was mostly, I think, to the fact that we had terrible wind miles 6-10. Other than that, the classics say start a little bit slower for a couple of miles, then run at your planned MP and somewhere around miles 18-20 you will see if you have some energy to keep the pace or speed up a little. Just don't start too fast - that's the thing. Especially, if it's your first. But, I believe, the main issue is not the tactics, like "what is the key - negative or positive splits?". The main factor is how you are prepared for the marathon, if the target time is manageable for you. That feeling comes with an experience, imo. Plus, of course, there are so many other factors :-) - weather, race profile, GI problems, not getting injured or sick before the race, etc... Concentrate on getting ready through training, don't bother with tactics much at this point - in any event even splits will be a pretty safe bet.

If your average needs to be 7:26, Then the most efficient pace for the whole race (if you can hold it) is 7:26. The reality is that most non-elite runners do not have the percent muscle mass (or the efficient liver function) that will allow them to have a level of glycogen that will last for the whole 26.2 miles. We start burning more and more muscle (rather than the glycogen in the muscle) for energy as the race goes on. Muscle for energy requires 20% more oxygen to produce the same level of energy – so as the race goes on it will be harder to hold that pace. That’s why, unless you are starting the race much slower than your “perfect” pace it will be hard to hold that pace thru the full marathon

I'm hoping to burn glycogen and fat during my race. If I have enough left in the tank at the end I will run hard as I can and may start to burn more muscle. Hopefully, I'll be close to the end at that point.